FIG. 1 is a schematic view illustrating the inner portion of a conventional slim-type optical disc drive. As shown in FIG. 1, the slim-type optical disc drive comprises a tray 110, a casing 112, and two sliding rails 140, 142. After the tray 110 is pushed into casing 112 of the optical disc drive, the tray 110 is fixed within the casing 112 by a locking unit (not shown). Under this circumstance, the tray 110 is in a tray-in status. Whereas, after an eject button on the tray 110 is pressed by the user, the locking unit will release the tray 110 and the tray 110 will be withdrawn from the optical disc drive. Under this circumstance, the tray 110 is in a tray-out status. In other words, if the tray 110 is not stored within the casing 112 and the optical disc drive is in the tray-out status, the tray 110 may be pulled out along the rails 140 and 142. After the tray 110 is pulled out, the optical disc loaded into the tray 110 may be replaced or the tray 110 may be pushed into the casing 112 (i.e. in the tray-in status).
Moreover, a daughter board (not shown) is fixed within the tray 110. A main board 160 is fixed on the casing 112. The main board 160 and the daughter board are electrically connected with each other to transmit signals through a U-shaped flexible cable 150. In other words, during the process of moving the tray 110, the daughter board is still in communication with the main board 160.
Generally, a spindle motor 120, a spindle motor driver chip (not shown), an optical pickup head 130 and an optical pickup head control chip (not shown) are mounted on the daughter board. In addition, a variety of circuits are installed on the main board 160. These circuits include for example an analog signal microprocessor, a digital signal process (DSP)/decoder microprocessor, a flash ROM chip, a SDRAM chip, and so on. The main board 160 and the daughter board are in communication with each other through the U-shaped flexible cable 150. Moreover, since the casing 112 is made of a metallic material, the casing 112 is also electrically connected to a ground voltage (Gnd).
After the optical disc drive confirms that the tray 110 is in the tray-in status, the optical disc drive is enabled. Whereas, after the optical disc drive confirms that the optical disc drive is disabled (spindle motor 120 and optical pickup head 130 are disabled), the tray 110 may be controlled to be in the tray-out status. Moreover, the optical disc drive is usually equipped with a limit switch 162 to detect the whether the tray 110 is in the tray-out status or the tray-in status.
Please refer to FIG. 1 again. The limit switch 162 is mounted on the main board 160. When the tray 110 is fixed within the casing 112 by the locking unit, the limit switch 162 is also pressed by the tray 110. Consequently, the limit switch 162 generates a first status signal. According to the first status signal, the circuits on the main board 160 may confirm that the tray 110 is in the tray-in status, and thus the optical disc drive will be enabled. Whereas, when the tray 110 is in the tray-out state, the limit switch 162 is no longer pressed by the tray 110. Consequently, the limit switch 162 generates a second status signal. Until the limit switch 162 is pressed by the tray 110 again and the first status signal is generated, the optical disc drive will be enabled again.
FIG. 2A is a schematic circuit diagram illustrating a first type of conventional limit switch. FIG. 2B is a schematic circuit diagram illustrating a second type of conventional limit switch. As shown in FIG. 2A, in a case that a touch terminal A of the limit switch 162 is not pressed, the second status signal at a high voltage level (Vcc) is outputted from an output terminal Out of the limit switch 162. Whereas, in a case that the touch terminal A of the limit switch 162 is pressed, the first status signal at a low voltage level (Gnd) is outputted from the output terminal Out of the limit switch 162.
As shown in FIG. 2B, in a case that a touch terminal A of the limit switch 162 is not pressed, the second status signal at the low voltage level (Gnd) is outputted from an output terminal Out of the limit switch 162. Whereas, in a case that the touch terminal A of the limit switch 162 is pressed, the first status signal at the high voltage level (Vcc) is outputted from the output terminal Out of the limit switch 162.
From the above discussions, the limit switch 162 is an important component of the optical disc drive for detecting whether the optical disc drive is in the tray-out status or the tray-in status. However, since the limit switch 162 is not cost-effective, it is necessary to provide another component to replace the limit switch 162.